Simplify the following expression: $r = \dfrac{p}{5} - \dfrac{p}{10}$
Answer: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $5$ and $10$ $\lcm(5, 10) = 10$ $ r = \dfrac{2}{2} \cdot \dfrac{p}{5} - \dfrac{1}{1} \cdot \dfrac{p}{10} $ $r = \dfrac{2p}{10} - \dfrac{p}{10}$ $r = \dfrac{2p -p}{10}$ $r = \dfrac{p}{10}$